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//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists purely as an
// implementation detail.  This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.

#ifndef Patternist_ComparisonPlatform_H
#define Patternist_ComparisonPlatform_H

#include "qatomiccomparators_p.h"
#include "qitem_p.h"
#include "qcommonsequencetypes_p.h"
#include "qdynamiccontext_p.h"
#include "qbuiltintypes_p.h"
#include "qitemtype_p.h"
#include "qpatternistlocale_p.h"

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

namespace QPatternist
{
    /**
     * @short Provides comparison functionality for classes that compare Items,
     * such as ValueComparison or MaxFN.
     *
     * Classes which need comparison functionalities should inherit from this class.
     *
     * The parameter of this template class is the class inheriting from ComparisonPlatform.
     *
     * The class inheriting ComparisonPlatform must implement the following function:
     * @code
     * AtomicComparator::Operator operatorID() const
     * @endcode
     *
     * @author Vincent Ricard <magic@magicninja.org>
     * @ingroup Patternist_expressions
     */
    template <typename TSubClass,
              bool issueError,
              AtomicComparator::ComparisonType comparisonType = AtomicComparator::AsValueComparison,
              ReportContext::ErrorCode errorCode = ReportContext::XPTY0004>
    class ComparisonPlatform
    {
    protected:
        /**
         * Makes ComparisonPlatform use the AtomicComparator @p comparator.
         */
        void prepareComparison(const AtomicComparator::Ptr &comparator);

        /**
         * Default constructor. Does nothing. It is implemented in order make template
         * instantiation easier.
         */
        inline ComparisonPlatform()
        {
        }

        /**
         * Utility function for fetching the appropriate AtomicComparator
         * for two atomic values of type @p type1 and @p type2, for the operator @p op.
         *
         * This function is used throughout the implementation, ranging from the ValueComparison
         * itself, to for example the aggregate functions.
         *
         * @param context the ordinary ReportContext, used for issuing errors.
         * @param type1 the type of the first operand value in a comparison for which the
         * returned AtomicComparator is intended for
         * @param type2 the type of the second operand value in a comparison for which the
         * returned AtomicComparator is intended for. Whether @p type1 and @p type2 corresponds
         * to what is the first second operand type does not have significance, the order
         * can be arbitrary
         */
        AtomicComparator::Ptr
        fetchComparator(const ItemType::Ptr &type1,
                        const ItemType::Ptr &type2,
                        const ReportContext::Ptr &context) const;

        /**
         * @short Compares @p i1 and @p i2 with operator @p op, using comparator @p
         * comp. All input arguments must be valid, and not @c null.
         *
         * This is a fast, raw function which has the requirement that the
         * caller knows what to compare and with what.
         */
        bool compare(const Item &i1,
                     const Item &i2,
                     const AtomicComparator::Ptr &comp,
                     const AtomicComparator::Operator op) const;

        /**
         * @short Compares @p it1 against @p it2, using comparator() and operatorID().
         *
         * If the comparator wasn't looked up at compile time, it will be
         * attempted before comparing. If this fails, errors are reported via
         * @p context.
         */
        bool
        flexibleCompare(const Item &it1,
                        const Item &it2,
                        const DynamicContext::Ptr &context) const;

        /**
         * @short like flexibleCompare(), but returns the result
         * as an AtomicComparator::Operator instead of @c bool.
         *
         * This is useful when it is significant how a less than comparison
         * fails; whether the two values are equal or greater than.
         */
        AtomicComparator::ComparisonResult
        detailedFlexibleCompare(const Item &it1,
                                const Item &it2,
                                const DynamicContext::Ptr &context) const;

        /**
         * @returns the AtomicComparator that has been allocated at compile time,
         * with prepareComparison(). If no AtomicComparator has been allocated
         * for some reason, this function returns @c null.
         */
        inline const AtomicComparator::Ptr &comparator() const
        {
            return m_comparator;
        }

        /**
         * Calling this function makes ComparisonPlatform use a comparator that
         * compares strings case insensitively.
         *
         * @see ValueComparison::isCaseInsensitiveCompare()
         */
        inline void useCaseInsensitiveComparator()
        {
            m_comparator = AtomicComparator::Ptr(new CaseInsensitiveStringComparator());
        }

    private:
        /**
         * @returns the operator that is used.
         */
        inline AtomicComparator::Operator operatorID() const
        {
            Q_ASSERT(static_cast<const TSubClass *>(this)->operatorID());
            return static_cast<const TSubClass *>(this)->operatorID();
        }

        /**
         * The comparator that is used for comparing atomic values. The AtomicComparator
         * that is used, depends on the static type of the operands. m_comparator can be
         * @c null if it wasn't possible to determine what comparator to use at compile time.
         */
        AtomicComparator::Ptr m_comparator;
    };

#include "qcomparisonplatform.cpp"

}

QT_END_NAMESPACE

QT_END_HEADER

#endif